The present invention relates to a thermal expansion valve used in a refrigeration cycle.
The example of a thermal expansion valve conventionally used in a refrigeration cycle is disclosed in Japanese Patent Laid-Open Publication No. 5-322380.
In FIG. 5, a prism-shaped valve body 510 comprises a first refrigerant passage 514 including an orifice 516, and a second refrigerant passage 519, mutually independent from one another. One end of the first refrigerant passage 514 is communicated to the entrance of an evaporator 515, and the exit of the evaporator 515 is communicated through the second refrigerant passage 519, a compressor 511, a condenser 512 and a receiver 513 to the other end of the first refrigerant passage 514. A bias means 517 which is a bias spring biasing a sphere-shaped valve means 518 is formed to a valve chamber 524 communicated to the first refrigerant passage 514, and the valve means 518 is driven toward or away from the orifice 516. Further, the valve chamber 524 is sealed by a plug 525, and the valve means 518 is biased through a support member 526. A power element 520 including a diaphragm 522 is fixed to the valve body 510 adjacent to the second refrigerant passage 519. An upper chamber 520a formed to the power element 520 defined by the diaphragm 522 is maintained airtight, with temperature-corresponding working fluid filled thereto.
A small pipe 521 extending out from the upper chamber 520a of the power element 520 is used to degasify the upper chamber 520a and to fill the temperature-corresponding working fluid to the upper chamber 520a, before the end of the pipe is sealed. One large-diameter end of a valve drive member 523 functioning as the heat-sensing driven member positioned within the valve body 510 extending from the valve means 518 and penetrating through the second refrigerant passage 519 is positioned in the lower chamber 520b of the power element 520, contacting the diaphragm 522. The valve drive member 523 transmits the temperature of the refrigerant vapor exiting the evaporator 515 and flowing through the second refrigerant passage 519 to the temperature-corresponding working fluid filled to the upper chamber 520a of the power element 520, which generates a working gas with a pressure corresponding to the transmitted temperature. The lower chamber 520b is communicated to the second refrigerant passage 519 through the space formed around the valve drive member 523 within the valve body 510.
Accordingly, the diaphragm 522 of the power element 520 uses the valve drive member 523 to adjust the valve opening of the valve means 518 against the orifice 516 (that is, the amount of flow of liquid-phase refrigerant entering the evaporator) according to the difference in pressure of the working gas of the temperature-corresponding working fluid filling the upper chamber 520a and the pressure of the refrigerant vapor exiting the evaporator 515 within the lower chamber 520b, under the influence of the biasing force of the bias means 517 provided to the valve means 518.
Moreover, the other end of the valve drive member 523 contacts the shaft 114, and thereby drives the valve means 518 via the shaft 114.
According to the above-mentioned prior-art thermal expansion valve, the power element 520 is exposed to external atmosphere, and the temperature-corresponding driving fluid in the upper chamber 520a receives influence not only from the temperature of the refrigerant exiting the evaporator and transmitted by the valve drive member 523 but also from the external atmosphere, especially the engine room temperature. Moreover, the above valve structure often caused a so-called hunting phenomenon where the valve responds too sensitively to the refrigerant temperature at the exit of the evaporator and repeats the opening and closing movement of the valve means 518. The hunting phenomenon is caused for example by the structure of the evaporator, the method of positioning the pipes of the refrigeration cycle, the method of using the expansion valve, and the balance with the heat load.
Conventionally, an adsorbent such as an activated carbon is utilized as means for preventing such hunting phenomenon. FIG. 6 is a cross-sectional view showing the thermal expansion valve disclosed in the above prior-art publication utilizing an adsorbent, the structure of which is basically similar to the prior-art thermal expansion valve of FIG. 5, except for the structure of the diaphragm and the structure of the valve drive member that functions as temperature sensing/pressure transmitting member. According to FIG. 6, the thermal expansion valve comprises a prism-shaped valve body 50, and the valve body 50 comprises a port 52 through which the liquid-phase refrigerant flowing through a condenser 512 and entering from a receiver tank 513 travels into a first passage 62, a port 58 sending the refrigerant traveling through the first passage 62 out towards an evaporator 515, an entrance port 60 of a second passage 63 through which the gas-phase refrigerant exiting the evaporator enters, and an exit port 64 through which the refrigerant exits toward the compressor 511.
The port 52 through which the refrigerant is introduced is communicated to a valve chamber 54 positioned on the center axis of the valve body 50, and the valve chamber 54 is sealed by a nut-type plug 130. The valve chamber 54 is communicated through an orifice 78 to a port 58 through which the refrigerant exits toward the evaporator 515. A sphere-shaped valve means 120 is mounted to the end of a small-diameter shaft 114 that penetrates the orifice 78, and the valve means 120 is supported by a support member 122. The support member 122 biases the valve means 120 toward the orifice 78 using a bias spring 124. The area of the flow path of the refrigerant is adjusted by varying the space formed between the valve means 120 and the orifice 78. The refrigerant sent out from the receiver 514 expands while passing through the orifice 78, and travels through the first passage 62 and exits from the port 58 toward the evaporator. The refrigerant exiting the evaporator enters from the port 60, and travels through the second passage 63 and exits from the port 64 toward the compressor.
The valve body 50 is equipped with a first hole 70 formed from the upper end portion along the axis, and a power element portion 80 is mounted to the first hole using a screw portion and the like. The power element portion 80 includes housings 81 and 91 that constitute the heat sensing portion, and a diaphragm 82 that is sandwiched between these housings and fixed thereto through welding. The upper end portion of a heat-sensing driven member 100 is welded onto a round hole or opening formed to the center area of the diaphragm 82 together with a diaphragm support member 82xe2x80x2, as shown in FIG. 7. The diaphragm support member 82xe2x80x2 is supported by the housing 81.
A two-phase refrigerant of gas and liquid that is either identical to the refrigerant flowing within passage 62 or having similar characters thereto is sealed inside the housing 81, 91 as a temperature-corresponding working fluid, which is sealed thereto by the small tube 21. Further, a plug body welded to the housing 91 can be used instead of the small tube 21. The diaphragm 82 divides the space within the housing 81, 91 and defines an upper chamber 83 and a lower chamber 85.
The heat-sensing/pressure transmitting member 100 is constituted of a hollow pipe-like member exposed to the second passage 63, with an adsorbent stored to the interior thereof. The upper end of the heat-sensing driven member 100 is communicated to the upper chamber 83, defining a pressure space 83a by the upper chamber 83 and the hollow portion 84 of the heat-sensing driven member 100. The pipe-shaped heat-sensing driven member 100 penetrates through a second hole 72 formed on the axis of the valve body 50, and is inserted to a third hole 74. A gap is formed between the second hole 72 and the heat-sensing driven member 100, through which the refrigerant within the passage 63 is introduced to the lower chamber 85 of the diaphragm.
The heat-sensing/pressure transmitting member 100 is slidably inserted to the third hole 74, and the end thereof is connected to one end of the shaft 114. The shaft 114 is slidably inserted to a fourth hole 76 formed to the valve body 50, and the other end thereof is connected to the valve means 120.
According to this structure, the adsorbent functioning as a time-constant retardant works as follows. When a granular activated carbon is used as the adsorbent 40, the combination of the temperature-corresponding working fluid and the adsorbent 40 is an absorption-equilibrium type, where the pressure can be approximated by a linear expression of the temperature within a considerably wide temperature range, and the coefficient of the linear expression can be set freely according to the amount of granular activated carbon used as the adsorbent. Therefore, the user of the thermal expansion valve can set the characteristic of the thermal expansion valve at will.
Accordingly, it takes a relatively long time to set the adsorption-equilibrium-type pressure-temperature equilibrium state when the temperature of the refrigerant vapor flowing out from the exit of the evaporator 515 is either rising or falling. In other words, the work efficiency of an air conditioning device is improved by stabilizing the performance of the air conditioning device capable of suppressing the sensitive operation of the thermal expansion valve caused by the influence of disturbance which may lead to the hunting phenomenon, by increasing the time constant.
FIG. 7 is a cross-sectional view explaining the structure where the diaphragm 82 is welded onto the opening portion formed to the upper end of the heat-sensing driven member 100. In FIG. 7, the diaphragm 82 is a stainless steel formed into a concentrical corrugated shape so that it can be deformed easily. Moreover, an opening is formed to the center portion thereof, and a rising portion 82a for guiding a reinforcement member is equipped to the upper area thereof in the drawing. Even further, the heat-sensing driven member 100 made of stainless steel has its end portion being formed into a collar, and a ring-like protrusion 100c together with a relief groove 100b is formed to the whole perimeter of the center area of the upper surface in the collar portion 100a, as shown in the drawing.
Further, a plate-shaped ring-like reinforcement member 100d is fit to the outer perimeter of the center rising portion 82a of the diaphragm 82 as shown in FIG. 7(a), and the reinforcement member is mounted on the protrusion 100c so that the reinforcement member 100d and the protrusion 100c are positioned in concentrical manners. Then, the member is pressurized and fixed in position using electrodes (not shown), and electric current is applied instantly to the upper and lower electrodes thereby welding the protrusion 100c as shown in FIG. 7(b). According to this step, the reinforcement member 100d is also welded to the diaphragm 82.
According to this structure, in order to prevent a gap from being generated between the diaphragm 82 and the flat surface of the collar of the heat-sensing driven member 100 when the protrusion 100c is melded, and to prevent the decreased strength portion from becoming the diaphragm fulcrum, a relief groove 100b having enough volume to store the melted metal is formed to both sides of the base portion of the protrusion 100c. 
A stopper member 82xe2x80x2 that supports the diaphragm 82 fixed to the heat-sensing driven member 100 is press-fit to the heat-sensing driven member through an opening formed thereto that is concentrical with the diaphragm 82, and contacts the collar portion 100a. The diaphragm 82 fixed between the collar 100a and the reinforcement member 100d through welding has its peripheral area sandwiched between the housing 81 and 91, with each end also being welded. Further, stainless steel material is used to form the housings 81, 91 and the reinforcement member 100d. 
However, according to the prior-art expansion valve, the structure where a diaphragm constituting a power element is welded onto a heat-sensing driven member with a hollow portion requires a reinforcement member, and further requires a rising portion to be formed to the diaphragm. This requires a large number of parts to be assembled and increased number of assembly steps, which leads to increased manufacturing cost. Moreover, according to the prior art structure, the positioning of the diaphragm, the reinforcement member and the hollow heat-sensing driven member is somewhat unstable, and it is difficult to match the axes of the diaphragm, the reinforcement member and the hollow heat-sensing driven member accurately.
The present invention aims at solving the above-mentioned problems of the prior art expansion valve. The object of the present invention is to provide a thermal expansion valve capable of being assembled with ease and being manufactured at low cost, wherein the diaphragm is inserted to the hollow heat-sensing driven member before welding the diaphragm to the hollow heat-sensing driven member.
In order to achieve the above objects, the present invention provides a thermal expansion valve including a heat-sensing driven member with a hollow portion formed to the interior thereof and having a heat sensing function positioned inside a refrigerant passage extending from an evaporator to a compressor, and a diaphragm inserted to said heat-sensing driven member through an opening formed to the center thereof, said diaphragm constituting a power element portion for driving the heat-sensing driven member; wherein the heat-sensing driven member comprises a collar formed to the end of the opening of the hollow portion and a protrusion formed to the collar, and the protrusion is used to weld the collar and the diaphragm together.
According to the present invention, the diaphragm is inserted to the heat-sensing driven member until it contacts the collar portion, where the diaphragm is fixed to the heat-sensing driven member and the collar portion is welded to the diaphragm, thereby simplifying the axis-matching arrangement.
In a preferred embodiment, the heat-sensing driven member is equipped with a diaphragm support member inserted thereto concentrically with the diaphragm, and the diaphragm is welded onto position between the collar and the diaphragm support member using a protrusion.
In a more preferable embodiment, the protrusion is formed to the whole perimeter of the surface of the collar that comes into contact with the diaphragm.
Further, the present invention provides a thermal expansion valve including a heat-sensing driven member with a hollow portion formed to the interior thereof and having a heat sensing function positioned inside a refrigerant passage extending from an evaporator to a compressor, a diaphragm inserted to the heat-sensing driven member through an opening formed to the center thereof, said diaphragm constituting a power element portion for driving the heat-sensing driven member, and a support member inserted to the heat-sensing driven member through an opening formed thereto that is concentrical with the opening of said diaphragm so as to support the diaphragm; wherein the heat-sensing driven member comprises a collar formed to the end of the opening of the hollow portion, the support member comprises a protrusion formed near the opening formed thereto, and the protrusion is used to weld the diaphragm between the collar and the support member.
According to the above-mentioned thermal expansion valve, the diaphragm contacts the protrusion formed to the support member and fixed to the heat-sensing driven member, and the protrusion is used to weld the diaphragm to position between the collar and the support member.
In a more preferable embodiment, the protrusion is formed to the surface of the support member that comes into contact with the diaphragm.
Even further, the present invention provides a thermal expansion valve including a heat-sensing driven member with a hollow portion formed to the interior thereof and having a heat sensing function positioned inside a refrigerant passage extending from an evaporator to a compressor, a diaphragm inserted to the heat-sensing driven member through an opening formed to the center thereof, said diaphragm constituting a power element portion for driving the heat-sensing driven member, and a support member inserted to the heat-sensing driven member through an opening formed thereto that is concentrical with the opening of said diaphragm so as to support the diaphragm; wherein the heat-sensing driven member comprises a collar formed to the end of the opening of the hollow portion, the collar further having a protrusion formed thereto; the support member comprises a protrusion formed near the opening formed thereto; and the two protrusions are used to weld the diaphragm between the collar and the support member.
Further, according to the above-mentioned thermal expansion valve, the diaphragm fixed to the heat-sensing driven member contacts the protrusions formed to the collar and the support member, respectively, and is welded between the collar and the support member using the two protrusions.
According to yet another embodiment, the protrusions mentioned above are each formed to the whole perimeter of the surface of the collar and the surface of the support member that come into contact with the diaphragm, respectively.
According to the thermal expansion valve having the structures mentioned above, it is possible to suppress hunting and to control the amount of refrigerant transmitted to the evaporator without having to change the basic structures of the prior-art thermal expansion valve using the heat-sensing driven member having an adsorbent placed inside the hollow area formed thereto.